What to expect from Dan Jennings

For the third season in a row, the Milwaukee Brewers found a rummage sale reliever among the heap of arms that were cut loose by their teams before Opening Day. In 2016, it was Carlos Torres, who went on to post a 2.73 ERA in 82.1 innings for Milwaukee that year. Last season it was Jared Hughes, and he subsequently authored a 3.02 ERA across 59.2 innings for the Brew Crew. For 2018, Slingin’ David Stearns has hitched his wagon to veteran left-hander Dan Jennings, who was in camp with the Rays this spring before getting the boot as a cost-cutting measure.

Jennings, who will turn 31 later on in April, began his professional career back in 2008 when he was a 9th round pick of the Marlins. He worked as a starter during his first year in rookie ball but converted to full-time reliever by the next season, a role he has remained in ever since. After working his way up the minor league ladder, Jennings made his MLB debut with Miami in 2012. He became a full-time big leaguer the next season and has spent that past five years pitching in The Show, getting traded from Miami to the White Sox in 2014, then from Chicago to Tampa Bay last July. He had signed a one-year, $2.375 mil deal to avoid arbitration, but since the Rays released him they only had to pay him about a quarter of that salary in the form of termination pay. The official terms of Jennings’ deal with Milwaukee have yet to be announced but it’s been reported that he signed for “less than $1 mil”, and the Brewers will have the option to keep him via arbitration next winter if they so choose. He would qualify for free agency on his own after the 2019 season.

For his career, Jennings has appeared in 312 contests and tossed 282.1 frames of 2.87 ERA baseball. He’s done that with less-than-stellar marks of 7.27 K/9 and 4.08 BB/9, though, so ERA estimators like FIP- (93) and DRA- (105) see the totality of his work as somewhere between slightly above-average to slightly below-average. Last season was a more or less typical Jennings campaign, with the southpaw finding his way into 77 contests between his two stops while logging a nifty 3.45 ERA across 62.2 innings. His strikeout and walks rates were right in line with his career averages, but as was the case with a good chunk of MLB pitchers last season, his home run rate was the worst of his career. The 1.15 HR/9 that he served up still came in below the league average, but both Jennings’ FIP and DRA came in more than a run higher than his actual earned run average.

Home run issues last year notwithstanding, Jennings has thrived throughout his career by keeping the ball on the ground. Relying heavily on his sinker has helped the lefty induce wormburners at a 55.4% rate in the big leagues, and only eight qualified relievers had a higher ground ball rate than Jennings’ 59.8% in 2017. Jennings will also throw a four-seam fastball that, like his sinker, averages about 90-91 MPH. He didn’t utilize the four-seamer at all last season, but has shown it so far in 2018 and he’s previously thrown it over 30% of the time in his career. His breaking ball is an effective slider that averaged 83.5 MPH in 2017 and has held opponents to just a .219 average against throughout his career. As alluded to above, Jennings isn’t a big strikeout pitcher - he’s put down 18.8% of hitters on strikes during his career, and induced a swinging strike 8.9% of the time. His high walk rates have been negated in the past by minuscule home runs totals (outside of 2017) and a deft ability at avoiding hard contact. Jennings hasn’t allowed hitters to register hard contact at a rate higher than 26% since 2014, and for his career batters have only made hard contact against him 27.4% of the time. He’s also sported an infield fly ball rate above 15% in each of the last three seasons prior to 2018.

As a left-handed sinker/slider specialist, one might assume that Jennings is best used a situational lefty on the mound. Throughout his career, though, that hasn’t necessarily been the case. Jennings has actually been slightly better against right-handers during his time in the big leagues, holding them to a .299 wOBA while lefties have gotten him for a .306 wOBA. The split was even in 2017, with both righties and lefties hitting for a .286 wOBA against Jennings. That has allowed Craig Counsell to use him as a regular bullpen arm rather than a LOOGY and even have him work multiple innings. So far this season Jennings has made three appearances and tossed 3.2 scoreless innings, striking out two while also issuing two walks.

Jennings was signed after the Boone Logan injury to give Milwaukee a second left-handed arm in the bullpen, but he’s more than just a left-handed specialist. The sinkerballing southpaw has been able to capably retire both righty and lefty hitters during his time in the big leagues and so far has been tasked to work full innings - or longer - as a member of Craig Counsell’s bullpen. It will be interesting to see how the relief roles shake out once Logan returns, but there’s no apparent reason to believe that Dan Jennings won’t be at least a league-average reliever for Milwaukee in 2018. By the end of the year, we should be able to add him to the pile of scrapheap successes that David Stearns has already built up during his time as Milwaukee’s General Manager.

Statistics courtesy of Fangraphs, Baseball Prospectus, and Baseball-Reference